Efficient methods and compositions for recovery of products from organic acid pretreatment of plant materials

ABSTRACT

The invention is directed to compositions and processes concerning efficient downstream processing of products derived from organic acids pretreatment of plant materials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.17/058,595 filed Nov. 24, 2020, which is a 35 U.S.C. 371 national stageof International Application Number PCT/CN2018/088698 filed May 28,2018, the full disclosure of each of which are incorporated herein byreference.

FIELD OF THE INVENTION

The invention is related to compositions and processes concerning; (i)recovery of organic acids from a cellulosic pulp derived from organicacids pretreatment of plant materials, (ii) treatment of celluloserecovered from a cellulosic pulp derived from organic acids pretreatmentof plant materials prior to conversion to glucose, (iii) separating andcleaning lignin from a lignin suspension derived from organic acidspretreatment of plant materials, (iv) recovery of organic acids from theaqueous phase of organic acids pretreatment of plant materials, (v)recovery of residual organic acids from hemicellulose-containingfractions derived from organic acids pretreatment of plant materials,and (vi) organic fertilizer produced from cellulose and hemicellulosicjuice derived from organic acid pretreatment of plant materials.

BACKGROUND OF THE INVENTION

The invention relates in a first aspect to a method for recoveringorganic acids from cellulosic pulp by a combined application of dryerand desolventizer. This aspect of the invention increases efficiency ofexisting organic acids pretreatment process by allowing recovery andreuse of the organic acids used to dissolve the hemicellulose and lignincontained in lignocellulosic plant materials. After the dissolving stepof organic acids pretreatment of plant materials, a mixture of solubleand insoluble parts is obtained. After separating the mixture intosoluble and insoluble fraction, a cellulosic pulp and extraction liquorare obtained. The cellulosic pulp represents about 62% of the solublefraction primarily composed of organic acids and water and 38% of theinsoluble fraction primarily comprised of undissolved cellulose.

Organic acids pretreatment processes suitable to application of thepresent invention are described in international patent publications WO2011/154293 and WO 2010/006840, the contents of which are herebyincorporated in their entirety. The present invention may also concernsrecovery of organic acids from an organic acids pretreatment processstep involving partial elimination of lignins to obtain a residualoverall level of lignins of 0.3% to 4%. Such step is described ininternational patent publication WO 2012/049054, the contents of whichis hereby incorporated in its entirety.

In such processes, the lost organic acids represent not only asignificant portion of the unit operational costs, but the unrecoveredorganic acids also have an impact on environmental considerations. Thus,efficient recovery of organic acids from the cellulosic pulp produced byorganic acids pretreatment of plant materials provides both economic andenvironmental advantages over existing methods.

In another aspect, the invention further relates to a process fortreating cellulose by a combination of neutralization and alkalization,wherein the cellulose is derived from existing processes for producingbioethanol or other products, comprising organic acids pretreatment ofplant materials. Such existing processes are described in U.S. patentpublication 2013-0183733, the contents of which is hereby incorporatedin its entirety.

Production of bioethanol via processes including the steps of organicacids pretreatment, involves an initial step to destructurelignocellulosic plant material by subjecting it to a mixture of formicacid, acetic acid and water, the next step involves separating cellulosefrom the other materials. In order to achieve the best possible yield ofenzymatic hydrolysis of the separated cellulose, a partial eliminationof lignin prior to the enzymatic hydrolysis step is disclosed, such atreatment of the cellulose, so as to eliminate the lignins in order toachieve a preferred lignin level, wherein the residual overall level oflignins is equal to approximately 1.65%, is carried out by means oftreating cellulose with sodium hydroxide, followed by a washing stepintended to eliminate the residual sodium hydroxide before enzymatichydrolysis.

Typically, treatment of cellulose derived from organic acidspretreatment of plant materials is carried out by adding sodiumhydroxide into the cellulose directly to adjust the pH to pH 10 to pH12, subsequently a separation step is carried out to separate themixture into the treated cellulose and the filtrate (mainly contain thesodium hydroxide and other soluble fractions). The cellulose produced bythe existing organic acids pretreatment process, contains residualorganic acids from the pretreatment process ranges between 0.5% to 5% ofthe dry cellulose by weight. Neutralization of these residual acidsconsumes large quantities of sodium hydroxide which directly result acost increases for bioethanol production and indirectly results in costincreases for treatment of the filtrate. Thus, a method for minimizingthe amount of sodium hydroxide required to reach the operational pHrange prior for subsequent treatment of cellulose represents aparticularly important advantage over existing methods.

In another aspect the invention relates to a process for separating andcleaning lignin from a lignin suspension derived from organic acidpretreatment of plant materials by use of centrifugation.

The organic acids pretreatment process uses an organic acids solution asreagent to dissolve the hemicellulose and lignin contained in plantmaterials, after separation, the extracted liquor is separated from themixture. The extracted liquor which is composed primarily of cellulose,dissolved hemicellulose, lignin, minerals, organic acids, water and theothers is concentrated by an evaporation system to remove part of theorganic acids and water to a dry matter content of 55% to 65%,calculated from the total weight of the concentrated extraction liquor.The existing processes are described in international patentpublications WO 2000/068494, WO 2009/092749, WO 2011/154293, and WO2015/185639, the contents of each which are incorporated by reference intheir entirety.

In such processes, a lignin suspension is typically obtained bydispersing the lignins in the mixture of concentrated extraction liquorand water and the separation of the lignin and sugars present in thelignin suspension are separated via a filter press. After separating thelignin, a pressed cake of lignin and sugar-comprising liquor areobtained. The pressed lignin cake is washed with water, or by acombination of air and water, to obtain a final washed lignin andwashing liquor.

However, the filter press cannot run continuously throughout the entireprocess, and therefore washing the cake using a filter press cannotproduce a homogeneous product due to structural limitations of thedevice. The filtered cake of lignin is a rectangle so that the wash pathacross the lignin cake is variable and generally inconsistent. Thepresent disclosure provides methods for centrifugal recovery of ligninsthereby reducing water usage and thus reducing energy consumption whileimproving recovery of lignin from lignin suspensions.

In another aspect the invention relates to a process for producinghemicellulosic juice by a combination of evaporation and stripping fromthe hemicellulosic mixture produced by organic acids pretreatment ofplant materials which is comprised largely of dissolved hemicellulose,organic acids and water. The organic acids pretreatment process use theorganic acids solution as a reagent to dissolve the hemicellulose andlignin contained in the lignocellulosic raw material in a relatively lowtemperature and atmospheric pressure, even in the following extractionliquor treatment process are carried out in a relatively low temperatureand at an atmospheric or vacuum pressure so as to prevent furfural to becreated.

Typically, the extraction liquor which consists of dissolvedhemicellulose, lignin, organic acids and water is concentrated by themulti-effect evaporation system to remove part of the organic acids andwater to a dry matter content of 55% to 65%, calculated from the totalweight of the concentrated liquor. The lignin contained in theconcentrated liquor is separated by an existing process for theseparation of lignins and sugars from an extracted liquor, in thisprocess, prior to separation of lignins and sugars, mixing theconcentrated liquor with water in equal parts by weight, the separatedlignin must be washed by water to remove the residual sugars, organicacids, the whole soluble materials and waters are collected together toform the hemicellulosic mixture of dissolved hemicellulose, organicacids and water produced in this process. Such processes are describedin international patent publications WO 2011/154293 and WO 2010/006840,the contents of each which are incorporated in their entirety.

Dissolved hemicellulose in the hemicellulosic mixture mainly comprisesxylose and arabinose which can be used to produce ethanol and otherindustrial products. However, organic acids present in thehemicellulosic mixture will inhibit conversion of xylose and arabinoseto ethanol and other industrial products. Thus, efficient removal oforganic acids from the hemicellulosic mixture to produce thehemicellulosic juice is particularly important for maximizing yield ofethanol from the available sugars within the hemicellulosic juice.

In another aspect the invention relates to recovering organic acids fromthe high water content organic acids solutions produced by organic acidspretreatment of plant materials processes. Typically the content oforganic acids in such processes are higher than 83% of the total weightof the solution. The organic acids serve as reagent to dissolve thehemicellulose and lignin contained in the lignocellulosic raw materialsin a relatively low temperature and atmospheric pressure to avoidproduction of furfural during the pretreatment process. Afterseparation, the liquor containing dissolved hemicellulose, lignin,organic acids, water and other constituents. The water, constituted ofthe waters in the organic acids solution and in the raw material, isconcentrated by an evaporation system to remove part of the organicacids with water which form the first stream of high water contentorganic acids solution.

The lignin contained in the concentrated liquor is separated by anexisting process for the separation of lignins and sugars from extractedliquor in this process, prior to the separation of lignins from theconcentrated liquor, mixing the concentrated liquor with waterprecipitates the lignins in the concentrated liquor, in equal parts byweight of the concentrated liquor. Subsequently, the separated lignin iswashed with water to remove residual sugars, organic acids and otherwater soluble components.

The whole soluble materials with the waters, the water remained in theconcentrated liquor, the water mixed in the concentrated liquor forprecipitating the lignin, and the water used as washing water, arecollected together to form a mixture consisting primarily of dissolvedhemicellulose, organic acids, the water (remained and added in theprocess) and other minor components. Such processes are described ininternational patent applications WO 2011/154293 and WO 2010/006840, thecontents of each which are incorporated in their entirety.

In order to efficiently remove the organic acids from the high watercontent organic acid solutions regardless of their source, a process acombination of evaporation with stripping is disclosed. The disclosedprocess comprises a first pass multi-effect evaporator to evaporate theorganic acids with water from the mixture partially, the condensate ofthe evaporator which mainly comprises organic acids and the water, formsthe second stream of high water content organic acids solution.

The concentrated organic acids mixture from evaporator is fed to astripping column wherein the organic acids are further removed to acontent of less than 2%, the condensate from the stripping column formsthe third stream of high water content organic acids solution.

The fourth stream of high water content organic acids is derived fromrecovery of organic acids from the cellulosic pulp which contains about62% of the soluble part (which largely consists of organic acids andwater), and about 38% of the insoluble part (which consists mainly ofcellulose) by use of a desolventizer adapted to utilize steam to removethe residual organic acids from dried cellulosic pulp. In this aspect ofthe present invention the condensate from the desolventizer forms thefourth stream of high water content organic acids solution.

In order to recycle the organic acids and the waters to the organicacids pretreatment process, the additional waters of these four streamsof high water content organic acids solution need to be removed fromthese four streams of high water content organic acids solution to meetthe requirement of water content for extraction and delignificationstep.

In another aspect the invention relates to a method for producingorganic fertilizers by utilizing stillage from cellulose andhemicellulosic juice.

This invention is based on organic acid pretreatment plant materialswherein the plant materials, particularly grain straw, serve as rawmaterial. The separation of lignocellulosic raw materials intocellulose, hemicellulosic juice and lignin by the organic acidpretreatment process, hydrolysis and fermentation of cellulose andhemicellulosic juice, and conversion of most of the cellulose andhemicellulosic juice into ethanol are described in international patentapplication WO 2015/185639, the contents of which is hereby incorporatedin its entirety.

Typically, in processes for producing fuel ethanol after fermentation,the mixture of fermented cellulose and hemicellulosic juice is fed to amash column of distillation system, where the ethanol is extracted toproduce the fuel ethanol. In such processes the residue is released fromthe bottom of the mash column. One consequence of the organic acidpretreatment process is that most of the nutritional constituents of thelignocellulosic raw material (protein, potassium, phosphate, etc.) isseparated into the hemicellulosic juice, and mixed with the fermentationmaterial (yeast, glycerol, etc.) as stillage. Use this stillage becomesa key problem, without a productive use, the stillage will be treated aswaste, and treatment of such waste is costly. Under existing processes,there is no good method being proposed. This aspect of the presentinvention provides a process for decanting and evaporating the stillagesolids to form the basis of a valuable organic fertilizer whilesimultaneously contributing vapor derived from the stillage liquid as athermocouple to the to the stillage solids evaporation system therebyproducing a thermodynamically efficient method of recovering andprocessing otherwise unproductive stillage.

SUMMARY OF THE INVENTION

A first aspect of the present invention discloses methods andcompositions for efficient, thorough and economic recovery of organicacids from cellulosic pulp by a combination of dryer and desolventizer.The method comprises a first step which uses the dryer to reduce theorganic acids to a content of 5% to 12%, calculated from the totalweight of the dried cellulosic pulp. At this level it is difficult tofurther remove organic acids by continued drying. To overcome thisdefect, the invention comprises a second step wherein a desolventizer isused to further remove the organic acids using direct steam as thedesolventizing medium to reduce the organic acid content to less than2%, relative to the total weight of the desolventized cellulosic pulp.

Another aspect of the present invention is to provide a process andcompositions for treating cellulose by a combination of neutralizationand alkalization that uses the minimum of sodium hydroxide possible toprepare cellulose for enzymatic digestion and means of recycling thesodium hydroxide liquor from the alkalization step to the neutralizationstep, using the minimum sodium hydroxide to decrease the cost ofbioethanol production and treatment of the attendant wastes.

Another aspect of the present invention provides lignin separation andcleaning process and compositions, using centrifugation which furthercomprises recycling specific portions of centrifugate and online washingto obtain pure lignin to decrease overall water consumption and obtainhigh quality lignin.

Another aspect of the invention is a process to efficiently andeconomically remove organic acids from the hemicellulosic mixture ofdissolved hemicellulose, organic acids, and water by combiningevaporation with stripping to produce a hemicellulosic juicecomposition. The process comprises in a first step a multi-effectevaporation system to partially evaporate the organic acids with waterto a dry matter content of 40% to 70%, calculated from the total weightof the concentrated hemicellulosic juice. The process further comprisesa second step wherein the concentrated hemicellulosic juice is fed to astripping column wherein the organic acids are further removed to acontent of less than 2%, calculated from the total weight of thehemicellulosic juice.

Another aspect of the present invention is a process for efficient andeconomic removal of water from high water content organic acidssolutions by a process comprising multi-column distillation to produce acomposition suitable for subsequent recycling within the organic acidspretreatment process. The process is characterized by a) adopting a twoto five columns distillation system to recover the organic acids, and b)feeding fresh steam only into the first column of the multi-columndistillation system, and c) providing the vapors released from previouscolumns to the subsequent columns as the thermal energy sequentially,and d) feeding one or more streams of high water content organic acidssolutions into different columns within the multi-column system tobalance the energy requirements for the columns comprising thedistillation system, and e) adjusting the content of the organic acidsin the condensate of the first column to minimize fresh steamconsumption, and f) recycling the total organic acids and the totalwaters discharged from the multi-column distillation system into theoverall process constituting organic acid pretreatment of plantmaterials, which can maximally reduce the energy, i.e., steamconsumption for recovering of the organic acids, meantime can recyclethe total organic acids and waters to the pretreatment process.

In another aspect of the present invention is a method to utilize thestillage of fermentation of cellulose and hemi-cellulosic juices toproduce an organic fertilizer composition efficiently and economically.Stillage is rich in organic matter and nutrients which meet therequirements as an organic fertilizer. The organic fertilizer canimprove quality of the soil as well as providing nutrients to plantse.g. grains. In contrast, chemical fertilizers can damage soil evenwhile providing nutrients to the plants. Organic fertilizer is animportant emerging direction for agriculture. This aspect of the presentinvention is characterized by the use of the stillage (fermentation byproducts) to produce valuable organic fertilizer by an efficient andeconomic method. The method comprises separating stillage by decantingto obtain a solid fraction of stillage and a thin stillage comprisingmore dilute fraction of stillage. The method further comprisesconcentrating the thin stillage by multi-effects evaporation system toobtain a concentrated stillage, mixing the solid fraction andconcentrated stillage to obtain a mixture, drying said mixture by dryerto obtain the organic fertilizer, the vapor released from the dryer asthe thermal energy of the multi-effect evaporation system, the freshsteam is fed to the multi-effect evaporation system as the supplementarythermal energy.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process diagram illustrating how organic acids are recoveredfrom cellulosic pulp by combination of dryer and desolventizer units.Cellulosic pulp (21) is introduced into the dryer unit (101) to obtaindried cellulosic pulp (22) and vapor (23). The vapor (23) is used toprovide thermal energy to the extraction liquor concentration system aswell as other operational units within the overall system. Driedcellulosic pulp (22) is fed to the desolventizer (103) to further removeorganic acids by utilizing direct steam (23) as the desolventizingmedium to obtain desolventized cellulosic pulp (24). The vapor (25) fromthe desolventizer unit is fed to condenser I (104). Non-condensing vapor(26) from condenser I (104) is fed to condenser II (105). The condensedvapor solution (27) from condenser I and the condensed vapor solution(28) from condenser II (105) may be combined to form the organic acidssolution (13).

FIG. 2 is a schematic illustrating the structure of the desolventizer(103). Dried cellulosic pulp (22) is fed into the top of thedesolventizer (103) through a feed inlet (106). The direct steam (23)sprays out from the holes of the plate (109) then goes out through thelayer of the dried cellulosic pulp, meantime the direct steam brings theresidual organic acids which is contained in the dried cellulosic pulpto form the organic acids vapor, the organic acids vapor is releasedfrom the vapor outlet (107) of the desolventizer (103). The releasedorganic acids vapor is fed into condenser I (104) and the uncondensedvapor within Condenser I (104) is fed into condenser II (105). Thecondensates of condenser I (104) and condenser II (105) form the organicacids solution (13). After desolventizing, the desolventized cellulosicpulp (24) is discharged by a rotary discharger (108).

FIG. 3 is a schematic illustrating the treatment of cellulose by acombination of neutralization and alkalization wherein the cellulose(21) is fed to the neutralization tank (101) where sodium hydroxide (23)and recycled sodium hydroxide liquor (22) are added to form theneutralized cellulose mixture (24). The neutralized cellulose mixture(24) is fed into press I (102) to obtain a filtrate (25) and theneutralized cellulose (26). The filtrate (25) is discharged to a wastewater treatment system (103), while the neutralized cellulose (26) isfed to the alkalized reactor (104). Within the alkalized reactor (104)sodium hydroxide (27) is added to obtain an alkalized cellulose mixture(28). The alkalized cellulose mixture (28) is fed into press II (105) toobtain the sodium hydroxide liquor (22) to recycle to the neutralizationtank and the final alkalized cellulose (29) product.

FIG. 4 is a process diagram illustrating a process for producing purelignin. In this process the third centrifugate (21) mixes withconcentrated extraction liquor (22) to form the mixture, the mixture isemulsified in the suspension tank (102) by using the continuous or batchemulsifier (101) to form stable lignin suspension (23). The ligninsuspension (23) is then fed into a centrifuge (103) where the ligninsuspension is separated into a lignin layer and a first centrifugate(25). The first centrifugate (25) is delivered to a multi-effectevaporation system (104) for hemicellulosic juice production. A firstwash water (27) is introduced to wash the lignin layer to produce asecond centrifugate (26). The first wash water may be the high acidcontent water from condenser I of the acids distillation unit (5) ofFIGS. 10-13. The second centrifugate (26) is also delivered to themulti-effect evaporation system (104) for hemicellulosic juiceproduction. A second wash water (28) is introduced to the lignin layerto produce at least a third centrifugate (21). The second wash water maycomprise the low acids content wash water from the other condensersexcept condenser I of the acids distillation unit (7) of FIGS. 10-13, orfresh water (29), or a mixture of both. The third and any subsequentcentrifugates may be combined and reintroduced into the suspension tank(102) to suspending the lignin. The washed lignin is discharged from thecentrifuge as pure lignin (24).

FIG. 5 illustrates the sequence of steps involved in producinghemicellulosic juice. Raw hemicellulosic juice (21) separated fromextraction liquor by lignin precipitation, filtration, and washing isfed into a multi-effect evaporation system (101). A concentratedhemicellulosic juice (22) and condensed organic acids (23) are producedby the multi-effect evaporator system. Fresh steam (26) and theconcentrated hemicellulosic juice (22) are introduced into the strippingcolumn (102) to further remove organic acids and obtain the strippedhemicellulosic juice (24) with an organic acid content of less than 2%of the total weight of the stripped hemicellulosic juice and the newlycondensed acids (25).

FIG. 6 graphically details a 2-effect evaporation and stripping system.Internal labels are described in Example 4.

FIG. 7 graphically details a 3-effect evaporation and stripping system.Internal labels are described in Example 4.

FIG. 8 graphically details a 4-effect evaporation and stripping system.Internal labels are described in Example 4.

FIG. 9 is a flow diagram of the process for recovering organic acidsfrom high water content organic acids solutions by multi-columndistillation. Raw lignocellulosic plant materials (11) are fed to theextraction step (101). Organic acids (12) are added to the plantmaterial at the extraction step (101) to dissolve the hemicellulose andlignin from the raw plant material (11) to obtain an extraction mixture(13). An extraction liquor (14) is produced by separation (102) ofsoluble and suspended particles from the extraction mixture wherein theinsoluble and unsuspended residue comprise the cellulosic pulp (15). Thecellulosic pulp (15) is dried in a dryer (109) to produce a driedcellulosic pulp (27) and the condensate from the dryer, includingorganic acids may be recycled in the extraction step (101). In thisprocess, the extraction liquor (14) is fed into the evaporation system(103) to partially remove residual organic acids and water to form afirst stream of high water content organic acids solution (1) and obtainconcentrated liquor (16). The concentrated liquor (16) is fed into thelignin separation (104) step, in this step the addition of water (17)precipitates the lignin, allowing separation of the lignin from theconcentrated liquor (16), obtaining the separated lignin (18) and thesoluble materials with the waters (19). The lignin requires washing withvarious wash waters (20) in a series of lignin washing steps (22) toremove residual sugars, organic acids and other water solubleconstituents. The water from the lignin washing step (105) and thesoluble materials with the wash water (19) are pooled to form a mixtureof hemicellulose, organic acids, water and other water solubleconstituents (23). To remove the organic acids from this mixture (23)and reduce the water content the mixture (23) is subject to multi-effectevaporation (106) The condensate of the multi-effect evaporator forms asecond stream of high water content organic acids solution (2).Following the multi-effect evaporation (106) the concentrated mixture(24) is fed into a stripping column (107) wherein the organic acids arefurther removed to a content of less than 2%, the condensate from thestripping column forms a third stream of high water content organicacids solution (3) and the hemicellulosic juice (25). To remove organicacids from the dried cellulosic pulp (15) a desolventizer (108) isadapted to use direct steam (26) to remove the residual organic acids.The condensate from the desolventizer forms a fourth stream of highwater content organic acids solution (4) and the desolventizedcellulosic pulp (28). The four streams of high water content organicacids solutions are fed into the multi-column distillation system (110)to reduce the water content. An aqueous acid solution (5) is obtainedwith an acid content of 0.5 to 10% in the condensate discharge from thetop of the first column. Subsequent columns produce condensate (7)discharge with acid content of 0.2% to 1%. Aqueous acid solutions (6)with an acid content of 5% to 15% comprise the bottom output of thefirst column. Where all acid percentages are calculated by weight.

FIG. 10 illustrates the details of a 2 column distillation system.Internal labels are described in Example 5.

FIG. 11 illustrates the details of a 3 column distillation system.Internal labels are described in Example 5.

FIG. 12 illustrates the details of a 4 column distillation system.Internal labels are described in Example 5.

FIG. 13 illustrates the details of a 5 column distillation system.Internal labels are described in Example 5.

FIG. 14 is a process diagram illustrating production of an organicfertilizer from fermentation stillage (21) from the bottom of a mashcolumn (100) of an ethanol distillation system. The stillage (21) is fedinto a decanter (101) to obtain a solid fraction (22) and a thinstillage (23). The thin stillage (23) is fed to the multi-effectevaporation system (102) to generate a concentrated stillage (24). Thesolid fraction (22) and the concentrated stillage (24) are fed into amixer (103) wherein the two fractions are mixed to obtain a mixture(25). The mixture (25) is fed into a dryer (104) to obtain a driedmixture (26) and this dried mixture (26) represents a high qualityorganic fertilizer. The vapor (27) released from the dryer (104) may befed into the multi-effect evaporator (102) to provide thermal energy forthe evaporation process, the fresh steam (28) is fed to the multi-effectevaporation system (102) as the supplementary thermal energy.

DETAILED DESCRIPTION OF THE INVENTION

Recovery of Organic Acids from Cellulosic Pulp

The first aspect of the present invention discloses methods andcompositions for efficient, thorough and economic recovery of organicacids from cellulosic pulp by a combination of dryer and desolventizer.The organic acids and desolventized cellulosic pulp are produced by aprocess comprising the steps of:

-   -   a) drying a cellulosic pulp produced from organic acids        pretreatment of plant material in a dryer to remove the organic        acids to a content of 3% to 18%, calculated from the total        weight of the dried cellulosic pulp, and,    -   b) capturing the vapor released from the dryer for use in the        extraction liquor concentration system and other organic acids        pretreatment operational systems as a source of thermal energy,        and    -   c) condensing the vapor in the extraction liquor concentration        system and other organic acids pretreatment operational systems        to form a first phase of the organic acids solution of the        organic acids pretreatment process, and    -   d) using direct steam in a desolventizer to further remove the        organic acids from the cellulosic pulp, to a content of less        than 2%, and    -   e) condensing the organic acids vapor released from the        desolventizer, to obtain a second phase of organic acids        solution of the organic acids pretreatment process.

This aspect of the invention relates to a method for recovering organicacids from cellulosic pulp derived from the organic acids pretreatmentprocess of plant material by a combination of dryer and desolventizer.The organic acids pretreatment process uses the organic acids as areagent to dissolve the hemicellulose and lignin contained in thelignocellulosic plant materials. After separating the cellulosic pulpfrom the mixture of the soluble part and insoluble part, the residuewhich includes the insoluble part is the cellulosic pulp.

The existing organic acids pretreatment process may include a step ofpartial elimination of the lignins to obtain a residual overall level oflignins of 0.3 to 4% of the total cellulosic pulp by dry weight. Thecontent of the organic acids in the cellulosic pulp may be 35% to 65%,calculated from the total weight of the cellulosic pulp. The content ofthe cellulose in the cellulosic pulp may be 30% to 50%, calculated fromthe total weight of the cellulosic pulp.

As shown in FIG. 1 the cellulosic pulp from the organic acidspretreatment process is fed to the dryer. The dryer reduces the organicacids to a content of 3% to 18%, calculated from the total weight of thedried cellulosic pulp, once the content of the organic acids is lowerthan 3%, the dryer cannot efficiently further remove organic acids, ifthe content of the organic acids is higher than 18%, the consumption ofdirect steam by the desolventizer is inefficient.

Drying of the cellulosic pulp is carried out by many forms of dryerswhich may include tube dryers, pneumatic dryers, spray dryers, rotarydisc dryers, and other dryer technologies known to those in the art; itis particularly preferable to utilize a tube dryer. The dryer step maybe carried out at a temperature of 90° C. to 150° C. After drying, thedried cellulosic pulp discharged from dryer is fed to the desolventizer.

The vapor which released from the dryer may be used for the extractionliquor concentration system as well as provide other systems withthermal energy. The condensates of the vapor from the dryer which iscondensed in the extraction liquor concentration system and othersystems form the first phase of organic acids solution and may be reusedin the organic acids pretreatment process.

In the desolventizer shown in FIG. 2, the organic acids are furtherremoved from the dried cellulosic pulp to a content of less than 2%,calculated from the total weight of desolventized cellulosic pulp. Thedesolventizer may utilize direct steam as the desolventizing medium toremove the organic acids furtherly from the dried cellulosic pulp. Thedesolventizer may further remove the organic acids by using direct steamas the desolventizing medium in step d) carried out at a temperature of90° C. to 150° C.

After the desolventization step, the desolventized cellulosic pulp canbe used to produce ethanol and other products.

The organic acids vapor also contains water released from thedesolventizer is recovered by the condensation system of the organicacids distillation system, wherein the organic acids are recovered foruse in the organic acids pretreatment process. The condensation systemis carried out by 1 to 3 condensers, preferably by 2 condensers.

Production of Alkalized Cellulose

This aspect of the invention relates to a process for treating celluloseby a combination of neutralization and alkalization to produce analkalized cellulose comprising the steps of:

-   -   a) neutralizing the organic acids contained in the cellulose        produced from organic acids pretreatment of plant material with        sodium hydroxide liquor recycled from step d) of the process to        form a neutralized cellulose mixture, and    -   b) separating neutralized cellulose from the neutralized        cellulose mixture with a press, the filtrate is directly        released to waste water treatment system, and    -   c) alkalizing the neutralized cellulose by addition of a sodium        hydroxide solution in a reactor to form an alkalized cellulose        mixture, and    -   d) separating the alkalized cellulose from the alkalized        cellulose mixture with a press, wherein the sodium hydroxide        liquor (filtrate of the alkalized cellulose mixture) comprises        sodium hydroxide for reuse in step a) of the process.

In this aspect of the invention, the cellulose produced from cellulosicpulp derived from the organic acid pretreatment processes and strippedof residual organic acids by the drying and desolventizing stepsdescribed above may still contain a residual level of organic acidsrepresenting is 0.5% to 5% of the total weight of the cellulose. In thisaspect of the invention such cellulosic pulp is further treated to forman alkalized cellulose by a process comprising neutralization andsubsequent alkalization.

As illustrated in FIG. 3, in step a) of the process residual organicacids contained in the cellulose are neutralized by adding sodiumhydroxide liquor recycled from separating the alkalized cellulose fromthe alkalized cellulose mixture in step d). The pH of the sodiumhydroxide liquor is pH 10 to pH 12. After addition of the sodiumhydroxide liquor to the cellulose, the pH of the cellulose mixture isadjusted to a range of 5 to 8 by addition of more sodium hydroxide asnecessary. Use of sodium hydroxide liquor recycled from the last stepsof the process for producing alkalized cellulose can decrease theoverall consumption of sodium hydroxide from 30% to 65% by weight,relative to current treatment processes.

In step b) the neutralized cellulose is separated from the neutralizedcellulose mixture by use of a press. The press may be a screw press orother type of press known to those of skill in the art. In thisseparation step, the neutralized cellulose mixture formed in step a) isseparated into two streams, one comprises the neutralized cellulose, theother comprises the filtrate. The neutralized cellulose has a dry solidcontent of 30% to 45%. The filtrate is directly released to a wastewater treatment system, the pH of the filtrate is pH 5 to pH 8, so thereis no need to adjust the pH by titration as in existing treatmentprocesses.

In step c), the neutralized cellulose is alkalized by adding a sodiumhydroxide solution to the neutralized cellulose in a reactor to a pH ofpH 10 to pH 12, at a temperature of 50° C. to 100° C. Under theseconditions the content of the lignin contained in the cellulose can bereduced to a level of 1% to 2.5%, calculated from the total weight ofthe cellulose.

In step d), the alkalized cellulose mixture is separated by use of apress. In this separation step, the alkalized cellulose mixture isseparated into two streams, one stream comprises the alkalizedcellulose, the other stream comprises the sodium hydroxide liquor.

The alkalized cellulose contains a dry solid content of 30% to 45%,calculated from the total weight of the alkalized cellulose. After awashing step, this alkalized cellulose can be hydrolyzed by cellulasewith a high conversion rate of cellulose to glucose.

The sodium hydroxide liquor may be recycled for neutralizing the organicacids in step a).

Production of Pure Lignin

This aspect of the invention relates to a process for separating andcleaning lignin from a lignin suspension by preceipitation andcentrifugation, comprising the steps of:

-   -   a) separating lignin from a lignin suspension produced from        organic acids pretreatment of plant material by batch or        continuous centrifugation, and    -   b) cleaning the precipitated lignin in the centrifuge by        multiple applications of wash solution onto the lignin layer        during centrifugation, to form multiple centrifugates, and    -   c) recovering a first centrifugate and a second centrifugate for        use in hemicellulosic juice concentration, and    -   d) recycling a third centrifugate for precipitating the lignin        in the concentrated extraction liquor into lignin suspension of        the organic acids pretreatment process.    -   e) discharging the lignin from the centrifuge.

The extraction liquor of this aspect of the invention is obtained fromexisting organic acids pretreatment processes wherein the hemicelluloseand lignin contained in plant materials are dissolved in the organicacids solutions from which the extraction liquor is derived. Theextracted liquor is separated from the mixture, the extracted liquorwhich comprises cellulose, dissolved hemicellulose, lignin, minerals,organic acids, water and the other minor constituents is concentrated bythe evaporation system to remove part of the organic acids and water toa dry matter content of 55% to 65%, calculated from the total weight ofthe concentrated extraction liquor.

Accord to the present invention, the separating equipment is acentrifuger, preferable a scraper centrifuger, which may be run incontinuous or batch mode. The centrifuger is equiped with a sprayingdevice which can evenly spray washing water onto the lignin layer toobtain a pure lignin.

As illustrated in FIG. 4, the third centrifugate from step d) mixes withconcentrated extraction liquor to form the mixture, the mixture is fedto the suspension tank in which the mixture is emulsified by using thecontinuous or batch emulsifier to form the stable lignin suspension. Thelignin suspension is then successively fed to the centrifuge, thecentrifuge then separates the lignin suspension to obtain the firstcentrifugate and a lignin layer. The first centrifugate which comprises10% to 60% of the total centrifugate volume is recovered for subsequentprocessing by the hemicellulosic juice production unit.

The spraying device delivers washing water which may include a mixtureof formic acid, acetic acid and water to provide an online wash of thelignin layer. In a preferred embodiment the centrifuge is continuouslyrotating. Under continuous rotation, the washing water can be evenlysprayed on the lignin layer to provide homogeneous cleaning of thelignin. During spraying, impurities are washed out by the washing water,the recovered washing water and the impurities form the secondcentrifugate which comprises 10% to 30% of the total centrifugate byvolume. The centrifuge continues to operate while subsequent washes areapplied to produce third and possible more centrifugates. The third andsubsequent centrifugates maycomprise 10% to 50% of total centrifugate byvolume. Once the final centrifugate is removed the lignin layer isdischarged from the centrifuger to obtain a pure lignin comprising 90%to 99% lignin by weight.

The washing water may comprise water or a mixture of formic acid, aceticacid and water, wherein the formic acid content of the mixture is 0% to30%, calculated from the total weight of the mixture, and the aceticacid content of the mixture is 0% to 20%, calculated from the totalweight of the mixture. The mixture of formic acid, acetic acid and watermay derive from the recovered organic acids from high water contentorganic acids solutions by acids distillation unit. In a preferredembodiment the initial washing water introduced into the certrifuge arederived from the high organic acids content washing water. In someembodiments the second washing water introduced into the centrifuge arederived from the low organic acids content washing water. In someembodiments fresh water comprises the washing water for the third andany subsequent wash procedures for cleaning the lignin layer to obtainthe pure lignin.

The first centrifugate and the second centrifugates may be recovered anddelivered to the subsequent hemicellulosic juice production unit, whilethe third and any subsequent centrifugate may be recycled to the ligninsuspending step to decrease water consumption for the initial ligninprecipitation step which consequently decreases energy consumption ofthe hemicellulosic juice production and organic acids recovery unit.

Production of Hemicellulosic Juice

This aspect of the invention relates to a process for producinghemicellulosic juice by a combination of evaporation and stripping,comprising the steps of:

-   -   a) introducing a hemicellulosic mixture comprised of dissolved        hemicellulose, organic acids, water and others produced by        organic acids pretreatment of plant material into a multi-effect        evaporation system, and    -   b) evaporating the hemicellulosic mixture within the        multi-effect evaporator to form a concentrated hemicellulosic        juice with a dry matter content of 40% to 70% (w/w), and    -   c) removing organic acids from the concentrated hemicellulosic        juice in a stripping column to form a hemicellulosic juice,        wherein the hemicellulosic juice comprises less than 2% (w/w)        organic acids.

This invention is based on the existing organic acids pretreatment ofplant materials process, wherein a mixture of formic acid and aceticacid or formic acid only are used to dissolve hemicellulose and ligninfrom the lignocellulosic raw plant materials, after an initialseparation step, the extraction liquor which comprises dissolvedhemicellulose, lignin, organic acids, water and other minor constituentsis separated from the remaining insoluble material (mainly comprisingcellulose).

After lignin precipitation, filtration and washing steps, the lignin isremoved from the extracted liquor, the remainder known as hemicellulosicjuice is comprised of dissolved hemicellulose, organic acids, water andother minor water soluble constituents.

The dissolved hemicellulose in the hemicellulosic juice is mainlycomprised of xylose and arabinose, which can be used to produce ethanoland other industrial products. Organic acids remaining in thehemicellulosic juice may inhibit the conversion of xylose and arabinoseto ethanol and other industrial products. In addition, such organicacids represent a loss of a costly reagent in the overall organic acidspretreatment process. This aspect of the invention specifically concernsproducing hemicellulose suitable for optimal conversion to ethanol withminimal residual organic acids by a process that can simultaneouslyrecover such organic acids present in hemicellulosic juice for use inthe organic acids pretreatment process.

The content of dissolved hemicellulose in hemicellulosic juice is 2% to20%, calculated from the total weight of the hemicellulosic mixture. Thecontent of organic acids in the hemicellulosic juice is 10% to 30%,calculated from the total weight of the hemicellulosic mixture. Step a)of the present invention is characterized in that the multi-effectevaporation system partially evaporates the organic acids with water toa dry matter content of 40% to 70%, calculated from the total weight ofthe concentrated hemicellulosic juice.

The multi-effect evaporation can decrease the steam/energy consumptionfor removing the organic acids and concentrating the hemicellulosicjuice. In some embodiments the multi-effect evaporation is characterizedby use of 2 to 4 effects evaporation systems as shown in FIGS. 6-8. In apreferred embodiment the process uses a 3 effects evaporation system.

In some embodiments the multi-effect evaporation of organic acids withwater is carried out at a temperature of 60° C. to 160° C. in the firsteffect evaporator. In some embodiments the multi-effect evaporation oforganic acids with water is carried out at a temperature of 25° C. to60° C. in the last effect evaporator.

The first evaporator of the multi-effect evaporation system may utilizethe vapor output from the top of the stripping column as the completesource or as a partial source of thermal energy. In each step of themulti-effect evaporation system, the vapor output from the top of theprevious evaporator may be utilized for thermal energy to drive thefollowing column to reduce the overall energy required by themulti-effect evaporation system.

As shown in FIGS. 6-8 the hemicellulosic mixture is fed in the firstevaporator and discharged from the first evaporator sequentially.

After the concentration of the hemicellulosic juice by the multi-effectevaporation system, the dry matter content of concentratedhemicellulosic juice which is discharged from the first evaporator is40% to 70% of the total weight of the concentrated hemicellulosic juice,the viscosity of the concentrated hemicellulosic juice is 200 mPas to1000 mPas, if the viscosity is higher than this range, the concentratedhemicellulosic juice it is too difficult to further remove the organicacids by evaporation.

This invention is further characterized by combining the multi-effectevaporation system with a stripping column. The concentratedhemicellulosic juice discharged from the multi-effect evaporation systemis fed to the top plate of the stripping column. The stripping columnutilizes direct steam as the stripping medium to remove the organicacids further to a content of less than 2% of the total weight of thestripped hemicellulosic juice.

The vapor output from the top of the stripping column may be used as thethermal energy of the first evaporator of the multi-effect evaporationsystem.

The stripped hemicellulosic juice discharged from the bottom of thestripping column is used as the final product, i.e. the hemicellulosicjuice, which can be used to produce ethanol and other industrialproducts.

Removal of Water from High Water Content Organic Acids Solutions

This aspect of the invention relates to a process for recovering organicacids from high water content organic acids solutions by multi-columndistillation, comprising,

-   -   a) adopting a two to five columns distillation system to recover        the organic acids, and    -   b) feeding fresh steam only into the first column of a        multi-column distillation system, the others columns utilize the        vapor released from the previous column as the thermal energy        sequentially, and    -   c) directing the vapors released from previous columns to the        subsequent columns as the thermal energy, so that the vapor        released from the first column will be fed into the second        column and the vapor released form the second column will be fed        into third column and so on through each column of the        distillation system, and    -   d) feeding one or more streams of high water content organic        acids solutions into different columns within the multi-column        system to balance the energy requirements for the columns        comprising the distillation system, and    -   e) adjusting the content of the organic acids in the condensate        of the first column to minimize fresh steam consumption, and    -   f) recycling the total organic acids and the total waters        discharged from the multi-column distillation system.

In this aspect of the invention, the high water content organic acidssolutions derived from organic acids pretreatment process of plantmaterial. Typically the content of the organic acids comprises more than83% of the total weight of the solution. Typically, during the organicacids pretreatment process, and as a consequence of the downstream stepsof cellulosic pulp processing and lignin and hemicellulosic sugarproduction in a relatively low temperature and atmospheric pressure,which lead to that there is no furfural created during the wholepretreatment process, as well as four streams of high water contentorganic acids solutions are generated. In order to recycle the organicacids in the high water content organic acids streams into the organicacids pretreatment process the water content must be reduced.

Recovering organic acids from the high water organic acids solution bydistillation requires very high energy inputs. Therefore, reducing theenergy required to recover and recycle organic acids is essential forcommercializing the organic acids pretreatment process.

In one embodiment the invention is characterized in that recoveringorganic acids from high water content organic acids solution by use of atwo to five column distillation system to maximize energy efficiency. Apreferred embodiment uses a four column distillation system.

The greater the number of columns, the less steam/energy is consumed bythe distillation system. However, the number of columns comprising thedistillation system is limited by the difference of temperature betweenthe columns of the distillation system. Surprisingly, we haveempirically discovered that if the system includes more than fivecolumns the difference in temperature between the columns is too smallto use the vapor released from the previous column as the steam/energyfor the following column in series.

After scientific analysis, two to five columns distillation system canbe suitable for recovering organic acids from high water content organicacids solution in this process, four columns distillation is the mostsuitable from the view of efficiency and economy.

Typically, organic acids pretreatment processes create four streams ofhigh water content organic acids solutions as described above. The term“high water content organic acids solution” means the water content ishigher than the required water content in the organic acids solutionused for dissolving plant materials in the organic acids pretreatmentprocess. Thus, to recycle the organic acids from the four high watercontent organic acids streams, the additional water added throughout thevarious process steps needs to be removed. In order to minimize theamount of steam/energy required for recovering organic acids from highwater content organic acids solutions by multi-column distillation it isnecessary to regulate the steam/energy used for each column so that itis suitable to the level of organic acids within the individual columnwithin the series.

The invention adopts two methods to accomplish this. First by feedingthe highest water content organic solution to the last column of thedistillation system and feeding the lowest water content organic acidssolution to the first column of the distillation system the energy inputinto the entire system is directed appropriately. Second, by regulatingthe organic acids content in the condensate discharged from the top offirst column from 0.5% to 10% of the total weight of the condensate byadjusting the quantity of the steam/energy introduced into the firstcolumn allows the consumption of the steam/energy across the wholedistillation system to be balanced. The condensate of the first columnorganic acids content of 0.5% to 10% can be diverted for use in thelignin precipitation step of the lignin production process.

In the system described here other columns in the series typicallyproduce condensates with an organic acids content of 0.2% to 1% of thetotal weight of the input condensates. These condensates can be recycledto the pretreatment process for washing lignin and other steps in thelignin production process.

In order to maintain an optimal temperature differential between thecolumns, the first column is operated out at a temperature of 120° C. to175° C., the last column is operated at a temperature of 50° C. to 95°C.

The organic acids solution discharged from the bottom of the firstcolumn has a water content of 5% to 15%, calculated from the totalweight of the organic acids solution, these organic acids solution canbe directly reused to the organic acids pretreatment process at theinitial step of solubilizing the raw plant material.

Organic Fertilizer

This aspect of the invention depicted in FIG. 14 relates to a method forproducing organic fertilizer from stillage created from cellulose andhemicellulosic juice, comprising the steps of:

-   -   a) separating stillage from cellulose and hemicellulosic juice        produced by organic acids pretreatment of plant material using a        decanter to obtain a solid fraction of the stillage and a thin        stillage, and    -   b) concentrating the thin stillage with a multi-effect        evaporation system to obtain a concentrated stillage wherein the        steam for the multi-effect evaporation system is supplied from        vapor released from the dryer in step d) of the process        optionally supplemented with fresh steam, and    -   c) mixing the solid fraction and concentrated stillage to obtain        a mixture, and    -   d) drying the mixture to obtain the organic fertilizer, wherein        the vapor released from the dryer is fed to the multi-effect        evaporation system as thermal energy for the multi-effect        evaporation system of the process.

This invention is based on the existing organic acids pretreatmentprocess. In the pretreatment process, the organic acids solution is usedas the extraction reagent to dissolve most of the lignin, hemicellulose,salts (mainly salts of potassium and the phosphate), protein and theother components of the lignocellulosic plant materials. Thepretreatment mixture is separated into the insoluble cellulosic pulp anda mixture of hemicellulosic juice and lignin. The cellulosic pulp isdried to obtain cellulose. The hemicellulosic juice and lignin mixtureis separated into hemicellulosic juice (containing hemicellulose, salts,protein and the other soluble constituents) and lignin. After hydrolysisand fermentation of cellulose and hemicellulosic juice, most of thecellulose and the hemicellulose included in the hemicellulosic juice areconverted into ethanol. After extraction of ethanol from the fermentedcellulose and hemicellulosic juice by distillation, residues offermented cellulose and hemicellulosic juice are discharged from thebottom of the mash column of the distillation system. The residues arethe stillage (by-product of the process).

The stillage contains many of the nutritive components (protein,potassium, phosphorus, calcium, magnesium, sodium, aluminum, etc.) fromthe lignocellulosic raw materials as well as additional nutritivecomponents comprising yeast, secondary metabolites produced by growth ofthe yeast during the fermentation, and residual yeast growth mediaincluding significant amounts of nitrogen, potassium, phosphorus andorganic substances. Such material represents all the requirements of anorganic fertilizer. Organic fertilizers are fertilizers derived fromanimal matter, animal excreta (manure), human excreta, and vegetablematter (e.g., compost and crop residues), in contrast, the majority offertilizers used in commercial agriculture are chemical fertilizersextracted from minerals (e.g., phosphate rock) or produced industrially(e.g., ammonia). Organic agriculture, as a system of farming, allows foruse of certain fertilizers and amendments and disallows others. Bothorganic and chemical fertilizers can provide significant boosts in plantyields however, organic fertilizers have more complete mineral profilesand cannot cause the kind of soil damage that can be inflicted bychemical fertilizers. Organic fertilizers are an important developingdirection for agriculture.

This process disclosed here in one embodiment uses agriculture residuesas the raw materials and the stillage produced in part by hydrolysis ofcellulose and hemicellulose recovered from the agriculture residues andfermentation of the sugars released by hydrolysis of cellulose andhemicellulose by yeast to produce an organic fertilizer.

The method is characterized in that the stillage is obtained from thebottom of the mash column of an ethanol distillation system. The drymatter content is 2% to 20%, calculated from the total weight of thestillage. In one embodiment a centrifuge is used to separate thestillage into a solid fraction and a thin stillage fraction. In apreferred embodiment the centrifuge is a decanter centrifuge.

After separation, the dry matter content of the solid fraction is 20% to45%, calculated from the total weight of the solid part of stillage. Thedry matter content of the thin stillage fraction is 1% to 15%,calculated from the total weight of the thin stillage.

The thin stillage may be concentrated by a multi-effect evaporationsystem. The multi-effect evaporation system may include 4 to 6 effectsevaporation system. In a preferred embodiment the multi-effectevaporation is a 5 effects evaporation system. In the multi-effectevaporation system, the vapor released from the top of the previousevaporator is utilized as the thermal energy of the following evaporatorto minimize the total energy for the multi-effect evaporation system.The thin stillage is fed into the last evaporator of the multi-effectevaporation system and discharged from the first evaporator of themulti-effect evaporation system. The multi-effect evaporation system iscarried out at a temperature of 30° C. to 150° C.

After the concentrating, the dry substance content of the concentratedstillage is 28% to 45%, calculated from the total weight of theconcentrated stillage.

The condensate of the vapor separated in the multi-effect evaporationsystem, which is obtained in step b), may be reused as process water.

The solid part and concentrated stillage are fed to a mixer, wherein thetwo parts are mixed to obtain the mixture of the solid fraction and theconcentrated stillage. The mixture of the solid part and theconcentrated stillage is dried by the dryer, preferably the tube dryer,to obtain the organic fertilizer. The dryer is operated at a temperatureof 80° C. to 160° C. The dry solid content of the organic fertilizer is50% to 80%, calculated from the total weight of the organic fertilizer.The vapor released from the dryer may be fed to the stillagemulti-effect evaporation system to provide thermal energy to themulti-effect evaporation system. After drying, the mixture of the solidpart and the concentrated stillage is dried and this dried mixture canbe used as the organic fertilizer.

The organic fertilizer contains the organic matter, protein, potassiumsalts, phosphate, the mineral substance and others. The organic mattercontent of the organic fertilizer is 30% to 65%, calculated from thetotal dry matter of the organic fertilizer. Total nutrient (calculatedbased on the formula that the nutrient=Nitrogen+Phosphoruspentoxide+potassium oxide) content of the organic fertilizer is 5% to30%, calculated from the total dry matter of the organic fertilizer. ThepH value of the organic fertilizer is 5.5 to 8.5. The water content ofthe organic fertilizer is 20% to 50%, calculated from the total weightof the organic fertilizer.

EXAMPLES Example 1

Organic Acid Recovery from Cellulosic Pulps

Corn straw was used as the lignocellulosic raw material. Cellulosic pulpwas obtained according to the organic acid pretreatment process. Theorganic acids composition is formic acid 26%, acetic acid content 59%,and 15% water, the temperature is 103° C., the solvation time is 240min. After separation, the cellulosic pulp is separated from the liquidfraction.

Approximately 5 kg of cellulosic pulp was recovered, the dry mattercontent was 38.0%, the content of the organic acids was 49.5% and thecontent of water was 12.5%, calculated from the total weight of thecellulosic pulp. The cellulosic pulp was fed to the dryer to obtain thedried cellulosic pulp, the drying temperature was 120° C. After drying,the organic acids content of the dried cellulosic pulp was 5.5%.

The dried cellulosic pulp was introduced into the desolventizer at afeed flowrate is 200 g/min, direct steam is introduced into the bottomof the desolventizer, the temperature of the steam was 120° C., and theflowrate of the direct steam feed to the desolventizer was 14.1 g/min.The desolventized cellulosic pulp was discharged from the desolventizer.

The organic acids content of the desolventized cellulosic pulp was 1.8%,calculated from the total weight of the desolventized cellulosic pulp.

A second cellulosic pulp derived from corn straw was prepared under thesimilar conditions as described above. In this trial however the dryertemperature was slightly lower (110° C.) while the flowrate of steam inthe desolventizer was increased to 26.3 g/min. The desolventizedcellulosic pulp produced under these conditions had an organic acidscontent of 1.95%.

In a third study wheat straw was used as the lignocellulosic rawmaterial and a cellulosic pulp was obtained according to the organicacid pretreatment process described above.

Approximately 5 kg of cellulosic pulp was recovered, the dry mattercontent was 37.5%, the content of organic acids was 50.2% and thecontent of water was 12.3%, calculated from the total weight of thecellulosic pulp. The cellulosic pulp was fed to the dryer to obtain thedried cellulosic pulp, the drying temperature was 115° C. After drying,the organic acids content of the obtained dried cellulosic pulp was6.7%.

The dried cellulosic pulp was introduced into the desolventizer at afeed flowrate is 200 g/min, direct steam is introduced into the bottomof the desolventizer, the temperature of the steam was 120° C., and theflowrate of the direct steam feed to the desolventizer was 16.8 g/min.The desolventized cellulosic pulp is discharged from the desolventizer.

The desolventized cellulosic pulp produced under these conditions had anorganic acids content of 1.91%.

Table 1 summarizes these data.

TABLE 1 Organic acid content of cellulosic pulps Desol- Dried ventizedcellulosic cellulosic Cellulosic pulp pulp pulp Direct Dry OrganicOrganic Organic steam matter acids Water acids acids Flow- contentcontent content content content rate (%) (%) (%) (%) (%) (g/min) Cornstraw 38   49.5 12.5 5.5 1.80 14.1 Corn straw 38   49.5 12.5 8.0 1.9526.3 Wheat straw 37.5 50.2 12.3 6.7 1.91 16.8

Example 2 Neutralization and Alkalization Treatment of Cellulose. Sample1 Method A:

Initially, 0.4 kg cellulose (lignin content was 4.1% and organic acidscontent was 1.56%) was fed to the reactor, the agitator was started andthe pH adjusted to 12 with a sodium hydroxide solution, which added 3.34L of additional water. The temperature of the reactor was maintained at80° C. and the reaction continued for 60 minutes.

When the reaction is ended, 9.16 g sodium hydroxide was consumed and thelignin content of the treated cellulose was 1.89%.

Method B:

In the initial neutralization step of a first processing run, 0.4 kgcellulose (lignin content was 4.1% and organic acids content was 1.56%)was fed to the reactor, the agitator was started and the pH adjusted topH 6.5 with a sodium hydroxide solution, which added 3.34 L ofadditional water. The temperature of the reactor was maintained at 80°C. and the reaction continued for 30 minutes. Following this reaction,the cellulose mixture was filtered and pressed.

In the alkalizing step the neutralized cellulose is added to analkalization reactor, the agitator is started, and the pH adjusted to pH12 with a sodium hydroxide solution, which added 3.34 L of additionalwater. The temperature of the reactor was maintained at 80° C. and thereaction continued for 30 minutes. Sodium hydroxide was added asnecessary to maintain the pH at pH 12. After 30 minutes the alkalizedcellulose mixture was filtered and pressed to obtain the sodiumhydroxide liquor and the alkalized cellulose. The sodium hydroxideliquor may be reused in the neutralization step in a second (subsequent)processing operations.

In a second processing run 0.4 kg of cellulose (with a lignin content of4.1% and an organic acids content of 1.56%) is fed into theneutralization reactor, the agitator is started, and the sodiumhydroxide liquor recovered from the alkalizing step of the firstprocessing run is used to adjust the pH to pH 6.8, the temperature ofthe reactor is maintained at 80° C. and the reaction continued for 30minutes. Following this reaction, the cellulose mixture was filtered andpressed.

The alkalizing step of the second (and subsequent) processing runscomprise the same as the steps described in the first round.Importantly, the sodium hydroxide liquor recovered after filtering andpressing the alkalized cellulose may be reused in the neutralizationstep in the next processing operation. In the second round of processingutilizing sodium hydroxide recovered from the first round the totalsodium hydroxide consumed was 4.58 g, the lignin content of the treatedcellulose was 1.85%.

Sample 2 Method A:

Initially, 0.4 kg cellulose (lignin content was 3.6% and organic acidscontent was 2.68%) was fed to the reactor, the agitator was started andthe pH adjusted to 12 with a sodium hydroxide solution, which added 3.34L of additional water. The temperature of the reactor was maintained at80° C. and the reaction continued for 60 minutes.

When the reaction is ended 12.4 g sodium hydroxide was consumed and thelignin content of the treated cellulose was 1.56%.

Method B:

In the initial neutralization step of a first processing run, 0.4 kgcellulose (lignin content was 3.6% and organic acids content was 2.68%)was fed to the reactor, the agitator was started and the pH adjusted topH 6.5 with a sodium hydroxide solution, which added 3.34 L ofadditional water. The temperature of the reactor was maintained at 80°C. and the reaction continued for 30 minutes. Following this reaction,the cellulose mixture was filtered and pressed.

In the alkalizing step the neutralized cellulose is added to analkalization reactor, the agitator is started, and the pH adjusted to pH12 with a sodium hydroxide solution, which added 3.34 L of additionalwater. The temperature of the reactor was maintained at 80° C. and thereaction continued for 30 minutes. Sodium hydroxide was added asnecessary to maintain the pH at pH 12. After 30 minutes the alkalizedcellulose mixture was filtered and pressed to obtain the sodiumhydroxide liquor and the alkalized cellulose. The sodium hydroxideliquor may be reused in the neutralization step in subsequent processingoperations.

In a second processing run 0.4 kg of cellulose (with a lignin content of3.6% and an organic acids content of 2.68%) is fed into theneutralization reactor, the agitator is started, and the sodiumhydroxide liquor recovered from the alkalizing step of the firstprocessing run is used to adjust the pH to pH 6.8, the temperature ofthe reactor is maintained at 80° C. and the reaction continued for 30minutes. Following this reaction, the cellulose mixture was filtered andpressed.

The alkalizing step of the second (subsequent) processing run comprisesthe same steps described in the first round. Importantly, the sodiumhydroxide liquor recovered after filtering and pressing the alkalizedcellulose may be reused in the neutralization step in the nextprocessing operation. In the second round of processing utilizing sodiumhydroxide recovered from the first round the total sodium hydroxideconsumed was 7.87 g, the lignin content of the treated cellulose was1.58%.

Sample 3 Method A:

Initially, 0.4 kg cellulose (lignin content was 3.8% and organic acidscontent was 4.52%) was fed to the reactor, the agitator was started andthe pH adjusted to pH 12 with a sodium hydroxide solution, which added3.34 L of additional water. The temperature of the reactor wasmaintained at 80° C. and the reaction continued for 60 minutes.

When the reaction is ended 17.9 g sodium hydroxide was consumed and thelignin content of the treated cellulose was 1.66%.

Method B:

In the initial neutralization step of a first processing run, 0.4 kgcellulose (lignin content was 3.8% and organic acids content was 4.52%)was fed to the reactor, the agitator was started and the pH adjusted to6.5 with a sodium hydroxide solution, which added 3.34 L of additionalwater. The temperature of the reactor was maintained at 80° C. and thereaction continued for 30 minutes. Following this reaction, thecellulose mixture was filtered and pressed.

In the alkalizing step the neutralized cellulose is added to analkalization reactor, the agitator is started, and the pH adjusted to pH12 with a sodium hydroxide solution, which added 3.34 L of additionalwater. The temperature of the reactor was maintained at 80° C. and thereaction continued for 30 minutes. Sodium hydroxide was added asnecessary to maintain the pH at pH 12. After 30 minutes the alkalizedcellulose mixture was filtered and pressed to obtain the sodiumhydroxide liquor and the alkalized cellulose. The sodium hydroxideliquor may be reused in the neutralization step in subsequent processingoperations.

In a second (subsequent) processing run 0.4 kg of cellulose (with alignin content of 3.8% and an organic acids content of 4.52%) is fedinto the neutralization reactor, the agitator is started, and the sodiumhydroxide liquor recovered from the alkalizing step of the firstprocessing run is used to adjust the pH to pH 7.1, the temperature ofthe reactor is maintained at 80° C. and the reaction continued for 30minutes. Following this reaction, the cellulose mixture was filtered andpressed.

The alkalizing step of the second (subsequent) processing run comprisesthe same steps described in the first round. Importantly, the sodiumhydroxide liquor recovered after filtering and pressing the alkalizedcellulose may be reused in the neutralization step in the nextprocessing operation. In the second round of processing utilizing sodiumhydroxide recovered from the first round the total sodium hydroxideconsumed was 13.3 g, the lignin content of the treated cellulose was1.63%.

Table 2 summarizes these sample data.

TABLE 2 Sodium hydroxide consumption for treating cellulose CelluloseSodium hydroxide consumption Acid Lignin Lignin Sodium Sodium contentcontent content hydroxide hydroxide before before after con- con- treat-treat- treat- sumption sumption Reduced ment ment ment of Plan A of PlanB ratio (%) (%) (%) (g) (g) (%) Sample 1 1.56 4.1 1.85 9.16 4.58 50.0%Sample 2 2.68 3.6 1.56 12.4 7.87 36.5% Sample 3 4.52 3.8 1.63 17.9 13.325.7%

Example 3 Lignin Production

Extraction liquor was obtained from the organic acid pretreatmentprocess, wherein the composition of the organic acids in thepretreatment comprises formic acid 26%, acetic acid content 59%, andwater 15%. The pretreatment temperature was 103° C. and the pretreatmentextraction duration was 240 min. After separation, the extraction liquorwas separated from the solid fraction, the extraction liquor wasconcentrated by evaporation, and the concentrated extraction liquorobtained. The dry matter content of the concentrated extraction liquorwas 60.1%, and the lignin content was 29.5% (the other components of theconcentrated extraction liquor are listed in Table 3).

1.40 kg of concentrated extraction liquor was combined with an equalweight of the fresh water (1.40 kg) and an emulsifier (SHW300R labemulsifier, Shanghai Shenghaiwei Electric Instruments Co., Ltd) operatedat 7500 rpm for about 30 min was used to produce a lignin suspension.The lignin suspension was introduced into a centrifuge, centrifuged for5 mins, and the first centrifugate (2.05 kg of liquid) and a solidlignin layer obtained. The first centrifugate is removed from thecentrifuge.

1.94 kg of wash water was fed into a spray device to wash the ligninlayer within the centrifuge. The washing water in the procedure includeswater and mixtures of formic acid, acetic acid and water. When feedingthe washing water to the centrifuge, an initial feed of 0.54 kg of highorganic acids content washing water comprising an organic acid contentof 5.92% was used, the second wash comprised 1.00 kg of low organicacids content washing water wherein the organic acid content was 0.8%,and a finally wash comprising 0.40 kg of fresh water was found to washthe lignin layer sufficiently to obtain pure lignin.

Following the initial centrifugation and discharge of the initialcentrifugate, the centrifuge continued to operate for 5 min, during thistime the first wash with high organic acids water was performed and thesecond centrifugate (0.54 kg) obtained. The centrifuge was operated foranother 5 mins during which time the second wash with low organic acidswater was performed and the third centrifugate 1.40 kg was obtained.After a subsequent third wash with fresh water a lignin layer comprising0.75 kg was obtained. The first centrifugate and the second centrifugatewere recovered and may be incorporated in subsequent hemicellulosicjuice production unit operations. The dry lignin was discharged from thecentrifuge, and the purity of the lignin determined to be 98.1% (thecomponents of the lignin at each stage of operation are shown in Table3).

TABLE 3 Components of concentrated extraction liquor, washing waters,and lignin (I) Concentrated Purity extraction Washing water of dryliquor H-water L-water H₂O Lignin lignin Lignin 29.54% 55.00% 98.1% H₂O 5.11% 94.09% 99.20% 100.00% 43.96% Cellulose  3.00%  0.03% Xylan  8.70% 0.10% Mineral  6.07%  0.07% Others 12.75%  0.14% Acetic acid 23.75% 5.87%  0.80%  0.57% Formic acid 11.08%  0.05%  0.13% Total 65.35% 5.92%  0.80%  1.04% Impurity Note: impurities include cellulose, xylan,trace mineral, acetic acid and formic acid.

The third centrifugate (1.40 kg) from above was recycled for use asdiluent of the concentrated extraction liquor to produce a ligninsuspension using the SHW300R lab emulsifier as described above. Theobtained lignin suspension was introduced into the centrifuger and thecentrifuger was operated as described above to yield a lignin layer ofabout 0.75 kg.

In this operation the first wash comprised 0.54 kg of high organic acidscontent wash water in which the organic acid content was about 10%. Thesecond wash comprised 1.00 kg the low organic acids content wash waterin which the organic acid content was about 2%, and a final washcomprising 0.40 kg of fresh water. All centrifuge operations andconditions were carried out as described above. As before, the first andsecond centrifugates may be recycled for use in subsequenthemicellulosic juice production unit operations. At the end of theoperation the lignin is discharged from the centrifuge. In this instancethe purity of the lignin was 97.2% (the components of the lignin at eachstage of operation are shown in Table 4).

TABLE 4 Components of concentrated extraction liquor, washing waters,and lignin (II) Concen- trated Purity extraction Washing water of dryliquor H-water L-water H₂O Lignin lignin Lignin 29.54% 55.00% 97.2% H₂O 5.11% 90.00% 98.00% 100.00% 43.40% Cellulose  3.00%  0.04% Xylan  8.70% 0.12% Mineral  6.07%  0.08% Others 12.75%  0.17% Acetic acid 23.75% 9.92%  2.00%  1.03% Formic acid 11.08%  0.08%  0.15% Total   65%   10%   2%    0%    2% Impurity Note: impurities include cellulose, xylan,trace mineral, acetic acid and formic acid. H-water indicates highorganic acids content wash water and L-water indicates low organic acidscontent wash water.

Once again, the third centrifugate (1.40 kg) from the operationdescribed above was recycled to dilute the concentrated extractionliquor to produce a lignin suspension by treatment with the SHW300R labemulsifier. The obtained lignin suspension was introduced into thecentrifuger and the centrifuger was operated as described above to yielda lignin layer.

In this operation the first wash comprised 0.54 kg of high organic acidscontent wash water in which the organic acid content was 5.92. Thesecond wash comprised 1.00 kg of low organic acids content washing waterin which the organic acid content was 0.8%, and a final wash comprising0.79 kg of fresh water. All centrifuge operations and conditions werecarried out as described above. As before, the first and secondcentrifugates may be recycled for use in subsequent hemicellulosic juiceproduction unit operations. At the end of the operation the lignin isdischarged from the centrifuge. In this instance the purity of thelignin was 98.8% (the components of the lignin at each stage ofoperation are shown in Table 5).

TABLE 5 Components of concentrated extraction liquor, washing waters,and lignin (III). Concentrated Purity extraction Washing water of dryliquor H-water L-water H₂O Lignin lignin Lignin 29.54% 55.00% 98.8% H₂O 5.11% 94.09% 99.20% 100.00% 44.34% Cellulose  3.00%  0.02% Xylan  8.70% 0.06% Mineral  6.07%  0.04% Others 12.75%  0.09% Acetic acid 23.75% 5.87%  0.80%  0.36% Formic acid 11.08%  0.05%  0.08% Total 65.35% 5.92%  0.80%  0.66% Impurity Note: impurities include cellulose, xylan,trace mineral, acetic acid and formic acid. H-water indicates highorganic acids content wash water and L-water indicates low organic acidscontent wash water.

Example 4 Hemiceullulosic Juice Processing

A concentrated hemicellulosic mixture was obtained from an initialhemicellulosic mixture comprising dissolved hemicellulose, organic acidswater, and other soluble constituents (16.4% dry matter content, 6.0%formic acid, 14.4% acetic acid, and 63.2% water) by use of an evaporator(100 mm diameter, 2 m height), using indirect steam to heat theevaporator to evaporate the organic acids and water from thehemicellulosic mixture.

The flowrate of the hemicellulosic mixture into the evaporator was 10.0kg/h, with an indirect steam flowrate of 6.2 kg/h, and an evaporationtemperature of 90° C., which produced a flowrate of the concentratedhemicellulosic mixture of 2.96 kg/h. The dry matter content of theconcentrated hemicellulosic mixture produced under these conditions was55.6%. The acids content of the concentrated hemicellulosic mixture was16.5%.

Feeding the resulting concentrated hemicellulosic mixture into the topof a stripping column (100 mm diameter, 2.5 m height), and feeding thedirect steam into the bottom of the stripping column, served topartially strip the organic acids present in the concentratedhemicellulosic into the direct steam. This produces the strippedhemicellulosic mixture. Adjusting the stripping specifications to adirect steam flowrate of 1.51 kg/h and a direct steam temperature of105° C. produced a flowrate of the stripped hemicellulosic mixture of2.46 kg/h. The dry matter content of the stripped hemicellulosic mixturewas 60.4%. The acids content of the stripped hemicellulosic mixture was1.64%.

Modeling the evaporation and stripping process with Aspen Plus software(Aspen Technology, Inc., Massachusetts, USA) allowed a number ofdifferent operational parameters to be explored based on regression ofthe vapor-liquid equilibrium with experimental data described above.

Using the model parameters described above, conditions and performancefor 2, 3 and 4 effects evaporation and stripping systems were simulatedfor concentration of hemicellulosic mixture comprising dissolvedhemicellulose, organic acids, and water and other constituents.

The flowsheets for the 2, 3, and 4 effects evaporation and strippingsystem are constructed for use by the Aspen Plus software, are shown inFIGS. 6-8, respectively. In these models the hemicellulosic mixture (21)comprising dissolved hemicellulose, organic acids, water and otherconstituents is evaporated by evaporator II and evaporator I and theconcentrated hemicellulosic juice (22) is obtained. The concentratedhemicellulosic juice (22) is fed to the top of the stripping column(102), fresh steam (26) is fed to the bottom of the stripping column(102) and the stripped hemicellulosic juice (24) is obtained. The vapordischarged from the top of the stripping columns and the additionalfresh steam (27) is used as a heat resource for evaporator I and thevapor discharged from the top of the stripping column and the additionalfresh steam (27) that is condensed within evaporator I is recovered ascondensed acid II (25). The vapor from evaporator I is used as a heatsource for evaporator II, while the vapor from evaporator I thatcondenses in evaporator II serves as condensed acid I (23). The samescenario involving use of vapor initially recovered from the strippingcolumn into evaporator I and vapor recovered from evaporator I servingas a heat source for evaporator II extends to systems that includeadditional multi-effect evaporator units as illustrated in FIG. 7 for a3-effect evaporator system and FIG. 8 for a 4-effect evaporator system,there is no need of fresh steam in FIG. 7 for a 3-effect evaporatorsystem, the more vapor (28) from the stripping column than the vaporneeded for the 4-effect evaporator system is discharged from the top ofthe stripping column is used to the other system.

The tables below present many of the observed and predicted parametersof each of the multi-effect evaporator systems described herein.

TABLE 6 Observed inputs to the evaporation system models Dry FormicAcetic Flow- matter acid acid Water rate content content content content(t/h) (%) (%) (%) (%) The 12.0 16.4% 6.0% 14.4% 63.2% hemi- cellulosicmixture

TABLE 7 Observed specification of the stripped hemicellulose juiceEvapor- Dry matter Total acids Water ation Flowrate content contentcontent effects (t/h) (%) (%) (%) 2 3.27 60.2% 0.53% 39.27% 3 3.25 60.5%1.65% 37.85% 4 3.27 60.1% 0.93% 38.97%

TABLE 8 Predicted steam consumption of evaporation and stripping systems2 effects 3 effects 4 effects Steam consumption of 3.85 2.75 3.23stripping (t/h) Steam consumption of 3.85 2.63 2.01 evaporation (t/h)Surplus steam (t/h) 0 0.12 1.22

TABLE 9 Predicted heat exchange surface area of evaporation systems 2effects 3 effects 4 effects Total heat exchange 887 1377 2269 surface(m²)

Example 5

Recovering Organic Acids from High Water Content Organic Acids Solutions

A high water content organic acids solution (27.6% formic acid, 51.5%acetic acid, and 20.9% water) was fed into a distillation column (90 mmdiameter, 3 m height, packing column) operating with a heat duty of 12.6MJ/h, a reflux ratio of 13.0, 1 atmosphere pressure, at a flow rate of4.0 kg/h. Under these conditions the condensate of the vapor releasedfrom the top of the column is produced at a flow rate of 0.41 kg/h whichcomprises 0.27% formic acid, 4.07% acetic acid, and 95.66% water. Thedistilled organic acids solution, which is discharged from the columnbottom, is obtained at a flow rate of 3.59 kg/h and comprises 30.7%formic acid, 56.9% acetic acid, and 12.4% water.

Modeling this process with the Aspen Plus software using the parametersdescribed above allows simulation of distillation systems comprising 2,3, 4, and 5 columns for separating water from high water content organicacids solutions. The flow sheets produced by the modelling software areshown in FIGS. 10-13 for 2-column, 3-column, 4-column, and 5-columndistillation systems, respectively.

The organic acids composition of the various input streams of high watercontent organic acids solutions originating from organic acidspretreatment processes are listed in Table 10.

TABLE 10 Organic acid composition of inputs to multi-column distillationsystems Flowrate Formic acid Acetic acid Water Stream (kg/h) content (%)content (%) content (%) 1 471.3 27.6% 49.1% 23.3% 2 270.7 5.8% 15.2%79.0% 3 80.6 7.6% 17.4% 75.0% 4 12.8 9.9% 18.9% 71.2% Note: The streamdesignation matches those depicted in FIG. 10 and described below.

The basic distillation process for a 2 column distillation system isillustrated in FIG. 10. Three of the four input streams are fed into arefed into the first distillation column (201). These streams are derivedfrom the hemicellulosic juice evaporation step (2), the hemicellulosicjuice stripping step (3), and the high water organic acids solution fromthe desolventizer step of cellulosic pulp processing (4). The condensateof vapor (7) discharged from the top of the first column (201) may berecovered for other unit operations. The concentrated mixture (301) isdischarged from the bottom of the first column (201) and fed into column2 (202). The remaining input stream (1) derived from the extractingliquor evaporation step of lignin production is also fed into column 2(202). The condensate of vapor (5) discharged from the top of the secondcolumn (202) may be recovered for other unit operations. The distilledorganic acids solution (6) is discharged from the bottom of the secondcolumn (202). The organic acid content of the various output streams ofa two-column distillation system are presented in Table 11.

TABLE 11 Organic acid composition of outputs of a 2-column distillationsystem Flowrate Formic acid Acetic acid Water Stream (kg/h) content (%)content (%) content (%) 5 129.8 0.0% 0.8% 99.2% 6 477.8 32.0% 60.0% 8.0%7 227.8 0.0% 0.8% 99.2% Note: The stream designation matches thosedepicted in FIG. 10 and described above.

A similar process representing the process flow within a 3 columndistillation system is depicted in FIG. 11. In this case the operationis similar in terms of input and output streams of the two column systemdescribed above. However, in this case the vapor condensates of thefirst two columns are pooled to form a single output stream (7 of FIG.11) and the distilled organic acids solution discharged from column 2(302) is fed into a third column (203) where the vapor condensate (5) isrecovered and the further distilled organic acids solution (6) isdischarged from the bottom of the third column (203). The organic acidcontent of the various output streams of a two-column distillationsystem are presented in Table 12.

TABLE 12 Organic acid composition of outputs of a 3-column distillationsystem Flowrate Formic acid Acetic acid Water Stream (kg/h) content (%)content (%) content (%) 5 78.4 0.0% 0.8% 99.2% 6 477.8 32.0% 60.0% 8.0%7 279.3 0.0% 0.8% 99.2% Note: The stream designation matches thosedepicted in FIG. 11 and described above.

Similarly, the process representing the process flow within a 4 columndistillation system is depicted in FIG. 12. The organic acid content ofthe various output streams of a two-column distillation system arepresented in Table 13.

TABLE 13 Organic acid composition of outputs of a 4-column distillationsystem Flowrate Formic acid Acetic acid Water Stream (kg/h) content (%)content (%) content (%) 5 49.8 0.0% 0.8% 99.2% 6 477.8 32.0% 60.0% 8.0%7 307.8 0.0% 0.8% 99.2% Note: The stream designation matches thosedepicted in FIG. 12.

The process representing the process flow within a 5 column distillationsystem is depicted in FIG. 13. The organic acid content of the variousoutput streams of a five-column distillation system are presented inTable 14.

TABLE 14 Organic acid composition of outputs of a 5-column distillationsystem Flowrate Formic acid Acetic acid Water Stream (kg/h) content (%)content (%) content (%) 5 37.5 0.0% 0.8% 99.2% 6 477.8 32.0% 60.0% 8.0%7 320.2 0.0% 0.8% 99.2% Note: The stream designation matches thosedepicted in FIG. 12.

According to the simulation flow sheets steam consumption can besignificantly reduced by the number of distillation columns present inthe system. The data supporting this observation is presented in Table15.

TABLE 15 Steam consumption profiles of 2-, 3-, and 4-column distillationsystems Heat duty Reduced ratio Type (MJ/h) (%) 2 column distillation1188 27.6% 3 column distillation 860.4 3 column distillation 860.4 20.0%4 column distillation 687.6

The indicated reduction in the thermal requirements of a two columnsystem relative to three column system is 27.6%, while the reduction inthe thermal requirements of a four column system are an additional 20%lower than those of three column system, with an overall reduction to42% of the thermal requirements of a two column system required for afour column system.

Interestingly, additional columns provide minimal energy improvements.See Table 16.

TABLE 16 Steam consumption profiles of 4- and 5-column distillationsystems Heat duty Reduced Type (MJ/h) ratio (%) 4 column distillation687.6 4.97% 5 column distillation 653.4

Example 6 Organic Fertilizer

In an initial experiment, corn straw was used as the lignocellulosicplant material source for organic acids treatment using formic acid andacetic acid to extract the hemicellulose and the lignin. The mixture ofhemicellulose and lignin was separated to obtain a cellulosic pulpfraction and an extraction liquor. The cellulosic pulp was treated topartially eliminate lignin and washed with water to obtain cellulose.The extraction liquor was concentrated to separate the lignin, after theseparation of the lignin, the residue was concentrated and stripped toobtain the hemicellulosic juice. The cellulose and hemicellulosic juicemixture was hydrolyzed and fermented of by adding cellulose enzymes andyeast, respectively, to produce ethanol. The ethanol was separated fromthe fermentate by distillation, the residual matter of the distillationconstitutes the stillage.

Stillage (2113 g comprising 9.23% dry matter content) was fed into adecanter to produce a solid fraction 61.4 g (comprising 38.0% dry mattercontent) and a thin stillage 2051.6 g (comprising 8.37% dry mattercontent) after decanting. The thin stillage was evaporated (in anevaporator operated at 110° C.) to obtain the concentrated stillage451.6 g (comprising 38.0% dry matter content). The solid fraction andconcentrated stillage were combined to obtain a mixture (513.0 g). Themixture was dried in a dryer operated at a temperature of 120° C. toobtain 335.1 g of a final organic fertilizer; with a dry matter contentof organic fertilizer of 58.2% and a pH of 6.1. The organic fertilizerhas a dry matter content of 58.2%, an organic matter content of 47.8%,and a total nutrient content of 5.86% (calculated based on a formulawherein Nutrient=Nitrogen+Phosphorus pentoxide+Potassium oxide),calculated from the total dry matter.

In a second trial to produce an organic fertilizer from stillage usingcorn straw as an initial input to the organic acids treatment process,stillage (2113 g comprising 9.23% dry matter) was fed into the decanter.After decanting a solid fraction 67.1 g (35.5% dry matter content) and athin stillage 2046 g (8.37% dry matter content) were obtained. The thinstillage was evaporated (in an evaporator operated at 105° C.) toproduce 456.7 g of a concentrated stillage with 37.5% dry mattercontent. The solid fraction and the concentrated stillage were combinedto produce 523.8 g of a mixture. The mixture was dried in a dryeroperated at 130° C. to produce 297.7 g of the final organic fertilizerwith a dry matter content of 65.5% at pH 6.0. The organic fertilizercontains 47.3% organic matter with a total nutrient content of 5.81%,calculated from the total dry matter.

In a third experiment to produce organic fertilizer from stillage, wheatstraw was used as an initial input to the organic acids treatmentprocess, stillage (1940 g comprising 9.38% dry matter) was fed into thedecanter. After decanting a solid fraction 59.5 g (37.0% dry mattercontent) and a thin stillage 1880.5 g (8.51% dry matter content) wereobtained. The thin stillage was evaporated (in an evaporator operated at115° C.) to produce 438.3 g of a concentrated stillage with 36.5% drymatter content. The solid fraction and the concentrated stillage werecombined to produce 497.8 g of a mixture. The mixture was dried in adryer operated at 140° C. to produce 244.3 g of the final organicfertilizer with a dry matter content of 74.5% at pH 6.2. The organicfertilizer contains 48.5% organic matter with a total nutrient contentof 6.12%, calculated from the total dry matter.

What is claimed is:
 1. A method for producing a fertilizer composition,the method comprising the steps of: a) separating stillage fromcellulose and hemicellulosic juice produced by organic acidspretreatment of plant material using a decanter to obtain a solidfraction of the stillage and a thin stillage, and b) concentrating thethin stillage with a multi-effects evaporation system to obtain aconcentrated stillage wherein the steam for the multi-effectsevaporation system is supplied from vapor released from the dryer instep d) of the process, and c) mixing the solid fraction andconcentrated stillage to obtain a mixture, and d) drying the mixture toobtain the organic fertilizer, wherein the vapor released from the dryeris fed to the multi-effect evaporation system as thermal energy for themulti-effect evaporation system of the process.
 2. The method accordingto claim 1, wherein the solid fraction comprises a dry solid content of20%-45% by weight.
 3. The method according to claim 1, wherein the thinstillage is concentrated in an evaporator comprising a 4 effectsevaporation system.
 4. The method according to claim 1, wherein the thinstillage is concentrated in an evaporator comprising a 5 effectsevaporation system.
 5. The method according to claim 1, wherein the thinstillage is concentrated in an evaporator comprising a 6 effectsevaporation system.
 6. The method according to claim 1, wherein the thinstillage is concentrated by a multi-effects evaporation carried out at atemperature of 30° C. to 150° C.
 7. The method according to claim 1,wherein the concentrated thin stillage produced by multi-effectsevaporation comprises a dry matter content of 28% to 45% by weight. 8.The method according to claim 1, wherein in that mixing the solidfraction and the concentrated stillage is carried out in a mixer.
 9. Themethod according to claim 1, wherein drying the mixture is carried outby a dryer selected from the group of tube dryer, pneumatic drier orsimilar drier.
 10. The method according to claim 1, wherein in themixture is dried to a dry solid content of 50% to 80% by weight.
 11. Themethod according to claim 1, wherein the mixture is dried at atemperature of 80° C. to 160° C.
 12. The method according to claim 1,wherein the organic fertilizer comprises an organic matter content of30% to 65%.
 13. The method according to claim 1, wherein the organicfertilizer comprises a total nutrient content of 5% to 30% by weight.14. The method according to claim 1, wherein the organic fertilizercomprises a water content of 20% to 50% by weight.
 15. The methodaccording to claim 1, wherein the organic fertilizer comprises a pH ofpH 5.5 to pH 8.5.
 16. The method according to claim 1, wherein in thestillage is obtained from cellulose and hemicellulosic juice produced bythe hydrolysis and fermentation of cellulose and hemicellulosic juiceseparately or collectively.
 17. The method according to claim 1, whereinthe steam for the multi-effects evaporation system is supplied fromvapor released from the dryer in step d) of the process supplementedwith fresh steam.
 18. An organic fertilizer composition obtained by amethod according to claim
 1. 19. The organic fertilizer compositionaccording to claim 18, wherein the organic fertilizer comprises anorganic matter content of 30% to 65% and/or comprises a total nutrientcontent of 5% to 30% by weight and/or comprises a water content of 20%to 50% by weight and/or comprises a pH of pH 5.5 to pH 8.5.